<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        html,body{height:100%}

        .bg1{
            background-color: #005de6;
        }

        .bg2{
            background-color: #4eccc4;
        }

        .bg3{
            background-color: thistle;
        }
    </style>
</head>
<body>

<div style="height: 100%" class="bg1">

</div>

</body>
</html>